Research ArticleExperimental Investigation on the Axially LoadedPerformance of Notched Hexagonal Concrete-FilledSteel Tube (CFST) Column

Jing Liu12 Zhe Li 3 and Fa-Xing Ding 2

1School of Civil Engineering Hunan City University Yiyang Hunan Province 413000 China2School of Civil Engineering Central South University Changsha Hunan Province 410075 China3School of Architecture and Art Central South University Changsha Hunan Province 410075 China

Correspondence should be addressed to Zhe Li lizhe88csueducn and Fa-Xing Ding dinfaxincsueducn

Received 15 July 2019 Revised 24 August 2019 Accepted 1 September 2019 Published 29 September 2019

Academic Editor Rosario Montuori

Copyright copy 2019 Jing Liu et al0is is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

0is study aimed to investigate the static performance of notched hexagonal concrete-filled steel tube (CFST) stub columnsthrough axial loading Notch length notch location and notch direction in 14 CFST stub columns were experimentally studiedStress process failure mechanism and ultimate strength in the notched CFSTcolumns were analyzed Results show that notchesin steel tubes can weaken the restraining effect of steel pipes on core concrete and induce a decrease in the ultimate strength ofspecimens 0e failure mode of components is greatly affected by notch orientation 0e notch is closed under axial compressionin the horizontally notched specimen and the slotting indicates outward buckling in the vertically notched specimen Based on thetest results a method for calculating the ultimate strength of notched hexagonal CFST columns was established 0is researchencourages the extensive application of these structures in civil engineering

1 Introduction

Concrete-filled steel tube columns are extensively used inengineering due to their simple joint structures convenientconnections and excellent flexural behavior CFST columnshave been widely explored worldwide and considerableprogress has been made [1ndash5]

However some CFST problems remain unsolved Somedamages weaken the mechanical properties of CFST col-umns thereby affecting the structural integrity and reducingthe working life of the columns (1) As with other metalstructures initial geometric and material defects exist in theexternal steel pipes of CFST members and CFST columnsare inevitably affected by corrosion and other external loadsupon use [1] (2) In some engineering projects such as thoseinvolving the connection of steel with a concrete compositebeam and CFSTcolumn joints notches must be cut onto thesteel pipe 0is method weakens the restraint effect of steelpipe on the core concrete at the joints Consequently thestiffness of the notched section decreases adversely affecting

the seismic performance of CFST columns at the joints[2ndash4]

0ese problems have been addressed in recent years (1)Regarding the geometric and material defects of CFSTcolumns Nia et al [6] investigated the influence of initialbuckling on the mechanical performance of a square steelpipe under oblique loading Sadovsky et al [7] investigatedthe effect of initial geometric imperfections on the bucklingstrength of steel members Zhang et al [8] studied the in-fluence of initial buckling on the energy dissipation of steelpipes under axial compression Nia et al [9] assessed theenergy absorption of a square pipe with a buckling initiator(2) Chang et al [10] and Ding et al [11] carried out axialcompression performance tests on circular or square CFSTcolumns with defects 0ey then proposed the ultimatebearing capacity calculation formula which is based onexperimental data fitting for such components Liu andYoung [12] studied the effect of buckling on steel squarehollow section compression members and analyzed thestrength of the test column with three different

HindawiAdvances in Civil EngineeringVolume 2019 Article ID 2612536 9 pageshttpsdoiorg10115520192612536

specifications Han et al [1] investigated the mechanicalproperties of square CFST columns under loading andchloride corrosion and then compared the ultimate strengthof loaded CFST columns with different specifications Chenet al [13 14] explored the axial compression property ofCFST columns and considered the hole rate concretestrength grade and slenderness ratio 0ey subsequentlyproposed the calculation method of ultimate bearing ca-pacity for damaged CFST columns Ding et al [15] in-vestigated the composite action of notched circular CFSTstub columns under axial compression through numericaland theoretical studies and then presented an empiricalformula to predict their ultimate capacity

In China hexagonal CFST columns have been applied inthe Gao Yin Finance Building in Tianjin and the CITIC Towerin Beijing [16] as shown in Figure 1 Studies on the effect ofhexagonal CFST columns on static performance have mostlyconsidered axial compression and bending [16ndash19] Notchedcircular and rectangular CFSTcolumns have been researchedbut notched hexagonal CFST columns remain rarely studied

0e present work focused on the static performance ofnotched hexagonal CFST columns based on our teamrsquosprevious research [11 15 17]0e objectives were as follows(1) to experimentally study 14 CFST stub columns and theirparameters including notch length notch location andnotch direction and (2) to establish a method for calculatingthe ultimate strength of notched hexagonal CFST stubcolumns

2 Experimental Study

21 Introduction of Test Twelve notched hexagonal CFSTcolumns and two intact CFST columns were included in theexperimental study Notch length notch location and notchdirection were considered and investigated All specimenshad the same section size and the material performance ofthe steel and concrete cube was tested through standardmethod before the experiment Table 1 shows the geometricproperties and characteristics of the CFST columns andFigure 2 presents a diagram of the notched hexagonal CFSTspecimens In the equation l and b are the length and widthof the notch respectively D is the side of the hexagon crosssection t is the thickness of the steel pipe H is the height ofthe specimen fs is the yield strength of the steel pipe andfcu is the compressive strength of the concrete cube

22 Loading Scheme 0e test adopted a 5000 kN pressFigure 3 shows the sketch of the test setup for the CFSTstubcolumn0e displacement-control loading system of the testcomprised the following the elastic stage in which 115 ofthe bearing capacity load was increased per load and theelastic-plastic stage in which 125 of the ultimate load wasincreased per load 0e load duration was approximately3min per level Deformation data were collected with anelectronic displacement meter 0e CFST columns wereconstantly loaded until failure 0e failure process and modewere observed and displacement and ultimate load wererecorded Each specimen test lasted for approximately 2 h

According to the characteristics of this specimen the testwas interrupted when the axial displacement reached0035H

23 Loading Phenomenon Figure 4 shows the failure modesfor test specimens 0e modes can be divided into two typesIn the hexagonal CFST column with horizontal slotting thenotch was closed under axial loading as shown inFigures 4(a) and 4(b) In the hexagonal CFST column withvertical slotting the slotting showed outward buckling asdemonstrated in Figures 4(c) and 4(d)

0e entire steel pipe was cut by the end of the experi-ment Figure 5 shows the failure of the core concrete (1) Inthe hexagonal CFST column with horizontal slotting con-crete crushing was observed near the notches as shown inFigures 5(a) and 5(b) (2) In the hexagonal CFST columnwith vertical slotting concrete breakage was severe (3) 0efailure phenomenon of the notched specimen in the cornerwas more evident than that in the side

24 Analysis of Test Results Figure 6 shows the load-dis-placement curve of the specimens 0e static tests of theCFST columns can be implemented in three stages elasticelastic-plastic and failure stages

241 Elastic Stage 0e hexagonal CFST columns are in theelastic phase when their strength is 07 of the ultimatestrength and the load-displacement curve is closely linear

242 Elastic-Plastic Stage 0e axial displacement growsnonlinearly as the axial load achieves the yield load 0elinearly increasing trend of axial displacement decreaseswith increasing load showing a slow increasing trendBuckling deformation does not appear in the steel pipe

243 Failure Stage 0e strength of CFST columns de-creases when the load exceeds the limit strength Moreoverdeformation intensifies in the slotting of the specimens withincreased axial deformation Bearing capacity increases tosome extent after the axial deformation of some specimensreaches approximately 0025H

Figure 6 compares the load-axial deformation curves ofthe notched and intact specimens 0e geometric and ma-terial parameters of the two specimens are the same 0estiffness of the two columns has no evident difference in theelastic stage 0e peak load of the notched specimen is lowerthan that of the intact specimen because the notch inducesthe premature failure of the steel pipe and greatly weakensthe restraint effect of the steel pipe on the concrete core

3 Effects of Three Parameters on the AxialCompression Performance of HexagonalCFST Column

31 Influence of Notch Length Figure 7 illustrates the effectsof slotting length on the mechanical properties of hexagonal

2 Advances in Civil Engineering

(a) (b)

Figure 1 Adhibition of hexagonal CFST columns in practical engineering projects (a) Gao Yin finance building (b) CITIC tower

Table 1 Geometric properties and characteristics of CFST columns

No Orientation Location l times b (mm) D times t times H (mm) fs fcu Nc Nt

1 HCFT1 Horizontal Sidewall 100times10 100times 4times 600 270 375 1468 14832 HCFT2 Horizontal Sidewall 60times10 100times 4times 600 270 375 1502 15293 HCFT3 Horizontal Sidewall 30times10 100times 4times 600 270 375 1527 15574 HCFT4 Horizontal Corner 100times10 100times 4times 600 270 375 1488 14565 HCFT5 Horizontal Corner 60times10 100times 4times 600 270 375 1514 15026 HCFT6 Horizontal Corner 30times10 100times 4times 600 270 375 1534 15387 HCFT7 Vertical Sidewall 100times10 100times 4times 600 270 375 1519 15308 HCFT8 Vertical Sidewall 60times10 100times 4times 600 270 375 1530 15589 HCFT9 Vertical Sidewall 30times10 100times 4times 600 270 375 1539 157410 HCFT10 Vertical Corner 100times10 100times 4times 600 270 375 1527 146811 HCFT11 Vertical Corner 60times10 100times 4times 600 270 375 1536 151612 HCFT12 Vertical Corner 30times10 100times 4times 600 270 375 1542 156913 HCFT13 Unimpaired mdash mdash 100times 4times 600 270 375 1555 157914 HCFT14 Unimpaired mdash mdash 100times 4times 600 270 375 1555 1580

Horizontalnotch

(a)

Verticalnotch

(b)

D2D2 D

H

l b

Centre Notch

2D

(c)

Figure 2 Diagram of notched hexagonal CFSTspecimens (a) Horizontal slotting (b) Vertical slotting (c) Dimension diagram of a notchedspecimen

Advances in Civil Engineering 3

CFST stub columns 0e notch lengths are 30 60 and100mm A long notch length leads to weak restraint effectand low ultimate strength of the specimen

In the horizontally notched specimens the carryingcapacities of the specimens with a notch length of 30mm are21 and 53 larger than those of specimens with notchlengths of 60 and 100mm respectively In the verticallynotched specimens the carrying capacities of specimenswith a notch length of 30mm are 22 and 48 larger thanthose of specimens with notch lengths of 60 and 100mmrespectively

32 Influence of Notch Location Figure 8 illustrates the ef-fects of slotting location on the mechanical performance ofhexagonal CFSTstub columns0e notches are located at thesideway and corner Given the weak overall mechanical

behavior of steel pipe and concrete in the corner the ulti-mate strength of the CFST column notched in the corner issmaller than that in the sideway In the horizontally notchedspecimens the carrying capacities of the specimens with asideway notch are 16 larger than those of specimens with avertical notch In the vertically notched specimens thecarrying capacity of the specimen with a sideway notch is24 larger than those of specimens with a corner notch

33 InfluenceofNotchDirection Figure 9 presents the effectsof slotting orientation on the work performance of hexag-onal CFST stub columns 0e notch orientations includehorizontal and vertical Given the weak overall mechanicalbehavior of steel pipe and concrete in the corner the ulti-mate bearing capacity of the corner-notched specimens issmaller than that in the middle one For sideway-notched

Displacementtransducer

N

N

(a) (b)

Figure 3 Sketch for testing the apparatus of CFST stub column (a) Test setup (b) Loading device

Notch

(a)

Notch

(b)

Notch

(c)

Notch

(d)

Figure 4 Failure modes for hexagonal CFSTcolumns (a) Horizontal notch in the sideway (b) Notch in the corner (c) Vertical notch in thesideway (d) Vertical notch in the corner

4 Advances in Civil Engineering

Concretefailure

(a)

Concretefailure

(b)

Concretefailure

(c)

Concretefailure

(d)

Figure 5 Core-concrete damage of typical specimens (a) Horizontal slotting in the sideway (b) Horizontal slotting in the corner (c)Vertical slotting in the sideway (d) Vertical slotting in the corner

0 4 8 12 16 200

450

900

1350

1800

HCFT1HCFT2

HCFT3 HCFT-14

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(a)

HCFT4HCFT5

HCFT6 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(b)

HCFT7HCFT8

HCFT9 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(c)

HCFT10HCFT11

HCFT12 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(d)

Figure 6 Load-displacement curve of hexagonal CFST columns (a) HCFT1simHCFT3 (b) HCFT4simHCFT6 (c) HCFT1simHCFT3 (d)HCFT4simHCFT6

Advances in Civil Engineering 5

specimens the carrying capacity of the specimens with avertical notch is 20 larger than that of specimens with ahorizontal notch For corner-notched specimens the car-rying capacity of specimens with a vertical notch is 13larger than that of specimens with a horizontal notch

4 Calculation of the Ultimate BearingCapacity of Notched CFST Columns

41 Bearing Strength Ding et al [17] proposed equation (1)to estimate the ultimate strength of notched hexagonal CFSTcolumns

N fcAc(1 + KΦ) (1)

where Ac and As are the section area of concrete and steeltube respectively fc is the compressive strength of concrete

fcu is the strength of standard cube concrete fs is the yieldstrength of steel tube Φ is a confinement index and K is acoefficient (K 13)

According to equation (1) the calculated ultimatebearing capacity of HCFT13 or HCFT13 is 1555 kN and theratio of measured to calculated values is 1016 0e resultsshow that equation (1) can predict the ultimate strength ofhexagonal CFST columns well 0e equation was then ap-plied as the basic computational formula for the ultimatestrength of the notched specimens

0e slotting length slotting orientation and slottinglocation considerably affect the ultimate strength 0ereforethe ultimate strength of notched CFST columns can beexpressed as

N fcAc 1 + K1Φ( 1113857 (2)

0 30 60 90 120600

900

1200

1500

1800

HCFT1~3HCFT4~6

Notch length

Axi

al lo

ad N

(kN

)

(a)

HCFT7~9HCFT10~12

0 30 60 90 120600

900

1200

1500

1800

Notch length

Axi

al lo

ad N

(kN

)

(b)

Figure 7 Influence of notch length on the ultimate strength of specimens (a) Horizontal notch (HCFT1simHCFT6) (b) Vertical notch(HCFT7simHCFT12)

0 1 2 3

Corner

HCFT1 HCFT4HCFT2 HCFT5HCFT3 HCFT6

Sideway

Notch location

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(a)

HCFT7 HCFT10HCFT8 HCFT11HCFT9 HCFT12

CornerSideway

0 1 2 3Notch location

600

900

1200

1500

1800A

xial

load

N (k

N)

(b)

Figure 8 Influence of notch location on the ultimate strength of specimens (a) Horizontal notch (HCFT1simHCFT6) (b) Vertical notch(HCFT7simHCFT12)

6 Advances in Civil Engineering

where K1 is the reduction factor which can be expressed as

K1 13 minus 06β1 + 02β2( 1113857β3 (3)

where β1 β2 and β3 are parameters related to slotting lengthslotting orientation and slotting location respectively andexpressed as

β1

l

S horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β2

b

H horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β3

13 sideway

1 corner

⎧⎪⎨

⎪⎩

(4)

where S which is the outer girth of square steel pipe is equalto 6D

Table 2 shows the calculated and experimental results forall the specimens Nt and Nc are the test strength andcalculated strength respectively 0e average NtNc ratio is1004 with a coefficient of variation of 0018 for springelement Hence equation (2) is acceptable

42 Confining Effect 0e notched steel pipe cannot exertsufficient restraint effect on the core concrete 0is structurealso has poor mechanical properties 0us estimating therestraint effect becomes essential 0e ultimate strength ofCSFT is the total of the contribution of the core concrete and

steel pipe and the composite effect between the core concreteand steel pipe It can be expressed as

N Asfs + Acfc + Fs (5)

where Fs is the composite effect between the core concreteand steel pipe

For notched columns only a part of the steel pipe cancarry the compression 0us the ultimate strength for anotched specimen can be defined as follows

Nc Asefs + Acfc + Fs (6)

For horizontal slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus l minus 2t)t + 2 Dt (7)

For vertical slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus b minus 2t)t + 2 Dt (8)

Hence a confinement factor defined in equation (9) wasapplied to estimate the restraint effect of a notched steel pipeon the core concrete

λ Fs

Nc (9)

Table 2 shows the confinement factor for all the notchedspecimens 0e results show the following (1) 0e con-finement factor of the horizontally notched specimen isgreater than that of the vertically notched specimen (2) 0econfinement factor of the sideway-notched specimen issmaller than the corner-notched ones (3) For horizontallynotched specimen the longer the slotting the greater is theconfinement factor In the vertically notched specimen theconfinement factor decreases when the duration of slottingincreases

HCFT1 HCFT7HCFT2 HCFT8HCFT3 HCFT9

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(a)

HCFT4 HCFT10HCFT5 HCFT11HCFT6 HCFT12

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(b)

Figure 9 Influence of notch orientation on the ultimate strength of specimens (a) Sideway notch (HCFT1simHCFT6) (b) Corner notch(HCFT7simHCFT12)

Advances in Civil Engineering 7

5 Conclusions

Fourteen CFST stub columns were included in the ex-periments and notch length notch location and notchdirection were considered 0e effects of the structure-failure pattern were further investigated and load-dis-placement curves were obtained Finally a method forcalculating the ultimate strength of notched hexagonalCFSTcolumns was established0emain conclusions are asfollows

(1) Compared with undamaged CFST columns undercompression the specimens showed failure modesthat differ according to the slotting orientation Forhorizontally notched specimens the notch is closedunder axial loading For vertically notched ones theslotting shows outward buckling phenomenon

(2) 0e ultimate strength of notched CFST columns isless than that of intact CFST because the notchedsteel pipe cannot provide sufficient restraint on thecore concrete For notched hexagonal CFSTcolumnthe ultimate strength is less than those of undamagedones 0e experimental study illustrates that slottinglength slotting orientation and slotting locationconsiderably affect the ultimate strength of notchedCFST columns

(3) A formula proposed by Ding et al [17] was used toestimate the ultimate strength of undamaged hex-agonal CFST columns On this basis we establish anequation to predict the ultimate strength of notchedhexagonal CFSTcolumns 0e calculation results areconsistent with the experimental data

Data Availability

All data used to support the findings of this study are in-cluded within the article 0ere are not any restrictions ondata access

Conflicts of Interest

0e authors declare that they have no conflicts of interest

Acknowledgments

0is research work was financially supported by the HunanEducation Department Foundation Funded Project Grantnos 18B438 and 14C0217 the Project funded by ChinaPostdoctoral Science Foundation Grant no 2018M632990 theNatural Science Foundation of Hunan Province China Grantnos 2018JJ3021 2018JJ2525 and 2019JJ20029 the NationalKey Research Program of China Grant no 2017YFC0703404and the National Natural Science Foundation of China Grantno 51308548

References

[1] L-H Han C Hou and Q-L Wang ldquoSquare concrete filledsteel tubular (CFST) members under loading and chloridecorrosion Experimentsrdquo Journal of Constructional Steel Re-search vol 71 no 4 pp 11ndash25 2012

[2] X Zhou G Cheng J Liu D Gan and Y Frank ChenldquoBehavior of circular tubed-RC column to RC beam con-nections under axial compressionrdquo Journal of ConstructionalSteel Research vol 130 no 3 pp 96ndash108 2017

[3] C Tian C Xiao T Chen and X Fu ldquoExperimental study onthrough-beam connection system for concrete filled steel tubecolumn-RC beamrdquo Steel and Composite Structures vol 16no 2 pp 187ndash201 2014

[4] J Pan PWang Y Zheng ZWang and D Liu ldquoAn analyticalstudy of square CFTcolumns in bracing connection subjectedto axial loadingrdquo Advances in Civil Engineering vol 2018Article ID 8618937 15 pages 2018

[5] R Montuori and V Piluso ldquoAnalysis and modelling of CFTmembers moment curvature analysisrdquo 6in-Walled Struc-tures vol 86 no 1 pp 157ndash166 2015

[6] A A Nia K F Nejad H Badnava and H R FarhoudildquoEffects of buckling initiators on mechanical behavior of thin-walled square tubes subjected to oblique loadingrdquo 6in-Walled Structures vol 59 no 11 pp 87ndash96 2012

[7] Z Sadovsky J Krivacek V Ivanco and A DuricovaldquoComputational modelling of geometric imperfections andbuckling strength of cold-formed steelrdquo Journal of Con-structional Steel Research vol 78 no 12 pp 1ndash7 2012

[8] X-W Zhang H Su and T-X Yu ldquoEnergy absorption of anaxially crushed square tube with a buckling initiatorrdquo In-ternational Journal of Impact Engineering vol 36 no 3pp 402ndash417 2009

Table 2 Confinement factor for all the notched specimens

No Ase (mm2) Ac (mm2) fs (MPa) fc (MPa) Nc (kN) Fs (kN) λ

HCFT1 2000 25980 270 274 1468 215 0147HCFT2 2160 25980 270 274 1502 206 0137HCFT3 2280 25980 270 274 1527 199 0130HCFT4 2000 25980 270 274 1488 235 0158HCFT5 2160 25980 270 274 1514 218 0144HCFT6 2280 25980 270 274 1534 205 0134HCFT7 2360 25980 270 274 1519 169 0111HCFT8 2360 25980 270 274 1530 180 0118HCFT9 2360 25980 270 274 1539 188 0122HCFT10 2360 25980 270 274 1527 177 0116HCFT11 2360 25980 270 274 1536 186 0121HCFT12 2360 25980 270 274 1542 192 0125HCFT13 2400 25980 270 274 1555 194 0125HCFT14 2400 25980 270 274 1555 194 0125

8 Advances in Civil Engineering

[9] A A Nia H Badnava and K F Nejad ldquoAn experimentalinvestigation on crack effect on the mechanical behavior andenergy absorption of thin-walled tubesrdquo Materials amp Designvol 32 no 6 pp 3594ndash3607 2011

[10] X Chang L Fu H-B Zhao and Y-B Zhang ldquoBehaviors ofaxially loaded circular concrete-filled steel tube (CFT) stubcolumns with notch in steel tubesrdquo 6in-Walled Structuresvol 73 no 12 pp 273ndash280 2013

[11] F-X Ding L Fu and Z-W Yu ldquoBehaviors of axially loadedsquare concrete-filled steel tube (CFST) Stub columns withnotch in steel tuberdquo 6in-Walled Structures vol 115 no 6pp 196ndash204 2017

[12] Y Liu and B Young ldquoBuckling of stainless steel square hollowsection compression membersrdquo Journal of ConstructionalSteel Research vol 59 no 2 pp 165ndash177 2003

[13] Z-P Chen Y-L Chen and M Zhong ldquoExperimental studyon axial compression capacity of concrete-filled square steeltubular columns with opening hole damagerdquo BuildingStructure vol 44 no 9 pp 9ndash14 2014 in Chinese

[14] Z-P Chen Y-L Chen andM Zhon ldquoExperimental study onmechanical properties of concrete-filled opening hole dam-aged steel tubular membersrdquo Industrial Construction vol 43no 2 pp 121ndash127 2013

[15] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof octagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 453ndash461 2016

[16] W Xu L-H Han and W Li ldquoPerformance of hexagonalCFST members under axial compression and bendingrdquoJournal of Constructional Steel Research vol 24 no 3pp 309ndash322 2017

[17] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof hexagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 502ndash513 2016

[18] M F Hassanein V I Patel and M Bock ldquoBehaviour anddesign of hexagonal concrete-filled steel tubular short col-umns under axial compressionrdquo Engineering Structuresvol 153 no 12 pp 732ndash748 2017

[19] B Evirgen A Tuncan and K Taskin ldquoStructural behavior ofconcrete filled steel tubular sections (CFTCFSt) under axialcompressionrdquo 6in-Walled Structures vol 80 no 7pp 46ndash56 2014

Advances in Civil Engineering 9

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Submit your manuscripts atwwwhindawicom

(a) (b)

Figure 1 Adhibition of hexagonal CFST columns in practical engineering projects (a) Gao Yin finance building (b) CITIC tower

Table 1 Geometric properties and characteristics of CFST columns

No Orientation Location l times b (mm) D times t times H (mm) fs fcu Nc Nt

1 HCFT1 Horizontal Sidewall 100times10 100times 4times 600 270 375 1468 14832 HCFT2 Horizontal Sidewall 60times10 100times 4times 600 270 375 1502 15293 HCFT3 Horizontal Sidewall 30times10 100times 4times 600 270 375 1527 15574 HCFT4 Horizontal Corner 100times10 100times 4times 600 270 375 1488 14565 HCFT5 Horizontal Corner 60times10 100times 4times 600 270 375 1514 15026 HCFT6 Horizontal Corner 30times10 100times 4times 600 270 375 1534 15387 HCFT7 Vertical Sidewall 100times10 100times 4times 600 270 375 1519 15308 HCFT8 Vertical Sidewall 60times10 100times 4times 600 270 375 1530 15589 HCFT9 Vertical Sidewall 30times10 100times 4times 600 270 375 1539 157410 HCFT10 Vertical Corner 100times10 100times 4times 600 270 375 1527 146811 HCFT11 Vertical Corner 60times10 100times 4times 600 270 375 1536 151612 HCFT12 Vertical Corner 30times10 100times 4times 600 270 375 1542 156913 HCFT13 Unimpaired mdash mdash 100times 4times 600 270 375 1555 157914 HCFT14 Unimpaired mdash mdash 100times 4times 600 270 375 1555 1580

Horizontalnotch

(a)

Verticalnotch

(b)

D2D2 D

H

l b

Centre Notch

2D

(c)

Figure 2 Diagram of notched hexagonal CFSTspecimens (a) Horizontal slotting (b) Vertical slotting (c) Dimension diagram of a notchedspecimen

Advances in Civil Engineering 3

CFST stub columns 0e notch lengths are 30 60 and100mm A long notch length leads to weak restraint effectand low ultimate strength of the specimen

In the horizontally notched specimens the carryingcapacities of the specimens with a notch length of 30mm are21 and 53 larger than those of specimens with notchlengths of 60 and 100mm respectively In the verticallynotched specimens the carrying capacities of specimenswith a notch length of 30mm are 22 and 48 larger thanthose of specimens with notch lengths of 60 and 100mmrespectively

32 Influence of Notch Location Figure 8 illustrates the ef-fects of slotting location on the mechanical performance ofhexagonal CFSTstub columns0e notches are located at thesideway and corner Given the weak overall mechanical

behavior of steel pipe and concrete in the corner the ulti-mate strength of the CFST column notched in the corner issmaller than that in the sideway In the horizontally notchedspecimens the carrying capacities of the specimens with asideway notch are 16 larger than those of specimens with avertical notch In the vertically notched specimens thecarrying capacity of the specimen with a sideway notch is24 larger than those of specimens with a corner notch

33 InfluenceofNotchDirection Figure 9 presents the effectsof slotting orientation on the work performance of hexag-onal CFST stub columns 0e notch orientations includehorizontal and vertical Given the weak overall mechanicalbehavior of steel pipe and concrete in the corner the ulti-mate bearing capacity of the corner-notched specimens issmaller than that in the middle one For sideway-notched

Displacementtransducer

N

N

(a) (b)

Figure 3 Sketch for testing the apparatus of CFST stub column (a) Test setup (b) Loading device

Notch

(a)

Notch

(b)

Notch

(c)

Notch

(d)

Figure 4 Failure modes for hexagonal CFSTcolumns (a) Horizontal notch in the sideway (b) Notch in the corner (c) Vertical notch in thesideway (d) Vertical notch in the corner

4 Advances in Civil Engineering

Concretefailure

(a)

Concretefailure

(b)

Concretefailure

(c)

Concretefailure

(d)

Figure 5 Core-concrete damage of typical specimens (a) Horizontal slotting in the sideway (b) Horizontal slotting in the corner (c)Vertical slotting in the sideway (d) Vertical slotting in the corner

0 4 8 12 16 200

450

900

1350

1800

HCFT1HCFT2

HCFT3 HCFT-14

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(a)

HCFT4HCFT5

HCFT6 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(b)

HCFT7HCFT8

HCFT9 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(c)

HCFT10HCFT11

HCFT12 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(d)

Figure 6 Load-displacement curve of hexagonal CFST columns (a) HCFT1simHCFT3 (b) HCFT4simHCFT6 (c) HCFT1simHCFT3 (d)HCFT4simHCFT6

Advances in Civil Engineering 5

specimens the carrying capacity of the specimens with avertical notch is 20 larger than that of specimens with ahorizontal notch For corner-notched specimens the car-rying capacity of specimens with a vertical notch is 13larger than that of specimens with a horizontal notch

4 Calculation of the Ultimate BearingCapacity of Notched CFST Columns

41 Bearing Strength Ding et al [17] proposed equation (1)to estimate the ultimate strength of notched hexagonal CFSTcolumns

N fcAc(1 + KΦ) (1)

where Ac and As are the section area of concrete and steeltube respectively fc is the compressive strength of concrete

fcu is the strength of standard cube concrete fs is the yieldstrength of steel tube Φ is a confinement index and K is acoefficient (K 13)

According to equation (1) the calculated ultimatebearing capacity of HCFT13 or HCFT13 is 1555 kN and theratio of measured to calculated values is 1016 0e resultsshow that equation (1) can predict the ultimate strength ofhexagonal CFST columns well 0e equation was then ap-plied as the basic computational formula for the ultimatestrength of the notched specimens

0e slotting length slotting orientation and slottinglocation considerably affect the ultimate strength 0ereforethe ultimate strength of notched CFST columns can beexpressed as

N fcAc 1 + K1Φ( 1113857 (2)

0 30 60 90 120600

900

1200

1500

1800

HCFT1~3HCFT4~6

Notch length

Axi

al lo

ad N

(kN

)

(a)

HCFT7~9HCFT10~12

0 30 60 90 120600

900

1200

1500

1800

Notch length

Axi

al lo

ad N

(kN

)

(b)

Figure 7 Influence of notch length on the ultimate strength of specimens (a) Horizontal notch (HCFT1simHCFT6) (b) Vertical notch(HCFT7simHCFT12)

0 1 2 3

Corner

HCFT1 HCFT4HCFT2 HCFT5HCFT3 HCFT6

Sideway

Notch location

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(a)

HCFT7 HCFT10HCFT8 HCFT11HCFT9 HCFT12

CornerSideway

0 1 2 3Notch location

600

900

1200

1500

1800A

xial

load

N (k

N)

(b)

Figure 8 Influence of notch location on the ultimate strength of specimens (a) Horizontal notch (HCFT1simHCFT6) (b) Vertical notch(HCFT7simHCFT12)

6 Advances in Civil Engineering

where K1 is the reduction factor which can be expressed as

K1 13 minus 06β1 + 02β2( 1113857β3 (3)

where β1 β2 and β3 are parameters related to slotting lengthslotting orientation and slotting location respectively andexpressed as

β1

l

S horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β2

b

H horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β3

13 sideway

1 corner

⎧⎪⎨

⎪⎩

(4)

where S which is the outer girth of square steel pipe is equalto 6D

Table 2 shows the calculated and experimental results forall the specimens Nt and Nc are the test strength andcalculated strength respectively 0e average NtNc ratio is1004 with a coefficient of variation of 0018 for springelement Hence equation (2) is acceptable

42 Confining Effect 0e notched steel pipe cannot exertsufficient restraint effect on the core concrete 0is structurealso has poor mechanical properties 0us estimating therestraint effect becomes essential 0e ultimate strength ofCSFT is the total of the contribution of the core concrete and

steel pipe and the composite effect between the core concreteand steel pipe It can be expressed as

N Asfs + Acfc + Fs (5)

where Fs is the composite effect between the core concreteand steel pipe

For notched columns only a part of the steel pipe cancarry the compression 0us the ultimate strength for anotched specimen can be defined as follows

Nc Asefs + Acfc + Fs (6)

For horizontal slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus l minus 2t)t + 2 Dt (7)

For vertical slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus b minus 2t)t + 2 Dt (8)

Hence a confinement factor defined in equation (9) wasapplied to estimate the restraint effect of a notched steel pipeon the core concrete

λ Fs

Nc (9)

Table 2 shows the confinement factor for all the notchedspecimens 0e results show the following (1) 0e con-finement factor of the horizontally notched specimen isgreater than that of the vertically notched specimen (2) 0econfinement factor of the sideway-notched specimen issmaller than the corner-notched ones (3) For horizontallynotched specimen the longer the slotting the greater is theconfinement factor In the vertically notched specimen theconfinement factor decreases when the duration of slottingincreases

HCFT1 HCFT7HCFT2 HCFT8HCFT3 HCFT9

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(a)

HCFT4 HCFT10HCFT5 HCFT11HCFT6 HCFT12

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(b)

Figure 9 Influence of notch orientation on the ultimate strength of specimens (a) Sideway notch (HCFT1simHCFT6) (b) Corner notch(HCFT7simHCFT12)

Advances in Civil Engineering 7

5 Conclusions

Fourteen CFST stub columns were included in the ex-periments and notch length notch location and notchdirection were considered 0e effects of the structure-failure pattern were further investigated and load-dis-placement curves were obtained Finally a method forcalculating the ultimate strength of notched hexagonalCFSTcolumns was established0emain conclusions are asfollows

(1) Compared with undamaged CFST columns undercompression the specimens showed failure modesthat differ according to the slotting orientation Forhorizontally notched specimens the notch is closedunder axial loading For vertically notched ones theslotting shows outward buckling phenomenon

(2) 0e ultimate strength of notched CFST columns isless than that of intact CFST because the notchedsteel pipe cannot provide sufficient restraint on thecore concrete For notched hexagonal CFSTcolumnthe ultimate strength is less than those of undamagedones 0e experimental study illustrates that slottinglength slotting orientation and slotting locationconsiderably affect the ultimate strength of notchedCFST columns

(3) A formula proposed by Ding et al [17] was used toestimate the ultimate strength of undamaged hex-agonal CFST columns On this basis we establish anequation to predict the ultimate strength of notchedhexagonal CFSTcolumns 0e calculation results areconsistent with the experimental data

Data Availability

All data used to support the findings of this study are in-cluded within the article 0ere are not any restrictions ondata access

Conflicts of Interest

0e authors declare that they have no conflicts of interest

Acknowledgments

0is research work was financially supported by the HunanEducation Department Foundation Funded Project Grantnos 18B438 and 14C0217 the Project funded by ChinaPostdoctoral Science Foundation Grant no 2018M632990 theNatural Science Foundation of Hunan Province China Grantnos 2018JJ3021 2018JJ2525 and 2019JJ20029 the NationalKey Research Program of China Grant no 2017YFC0703404and the National Natural Science Foundation of China Grantno 51308548

References

[1] L-H Han C Hou and Q-L Wang ldquoSquare concrete filledsteel tubular (CFST) members under loading and chloridecorrosion Experimentsrdquo Journal of Constructional Steel Re-search vol 71 no 4 pp 11ndash25 2012

[2] X Zhou G Cheng J Liu D Gan and Y Frank ChenldquoBehavior of circular tubed-RC column to RC beam con-nections under axial compressionrdquo Journal of ConstructionalSteel Research vol 130 no 3 pp 96ndash108 2017

[3] C Tian C Xiao T Chen and X Fu ldquoExperimental study onthrough-beam connection system for concrete filled steel tubecolumn-RC beamrdquo Steel and Composite Structures vol 16no 2 pp 187ndash201 2014

[4] J Pan PWang Y Zheng ZWang and D Liu ldquoAn analyticalstudy of square CFTcolumns in bracing connection subjectedto axial loadingrdquo Advances in Civil Engineering vol 2018Article ID 8618937 15 pages 2018

[5] R Montuori and V Piluso ldquoAnalysis and modelling of CFTmembers moment curvature analysisrdquo 6in-Walled Struc-tures vol 86 no 1 pp 157ndash166 2015

[6] A A Nia K F Nejad H Badnava and H R FarhoudildquoEffects of buckling initiators on mechanical behavior of thin-walled square tubes subjected to oblique loadingrdquo 6in-Walled Structures vol 59 no 11 pp 87ndash96 2012

[7] Z Sadovsky J Krivacek V Ivanco and A DuricovaldquoComputational modelling of geometric imperfections andbuckling strength of cold-formed steelrdquo Journal of Con-structional Steel Research vol 78 no 12 pp 1ndash7 2012

[8] X-W Zhang H Su and T-X Yu ldquoEnergy absorption of anaxially crushed square tube with a buckling initiatorrdquo In-ternational Journal of Impact Engineering vol 36 no 3pp 402ndash417 2009

Table 2 Confinement factor for all the notched specimens

No Ase (mm2) Ac (mm2) fs (MPa) fc (MPa) Nc (kN) Fs (kN) λ

HCFT1 2000 25980 270 274 1468 215 0147HCFT2 2160 25980 270 274 1502 206 0137HCFT3 2280 25980 270 274 1527 199 0130HCFT4 2000 25980 270 274 1488 235 0158HCFT5 2160 25980 270 274 1514 218 0144HCFT6 2280 25980 270 274 1534 205 0134HCFT7 2360 25980 270 274 1519 169 0111HCFT8 2360 25980 270 274 1530 180 0118HCFT9 2360 25980 270 274 1539 188 0122HCFT10 2360 25980 270 274 1527 177 0116HCFT11 2360 25980 270 274 1536 186 0121HCFT12 2360 25980 270 274 1542 192 0125HCFT13 2400 25980 270 274 1555 194 0125HCFT14 2400 25980 270 274 1555 194 0125

8 Advances in Civil Engineering

[9] A A Nia H Badnava and K F Nejad ldquoAn experimentalinvestigation on crack effect on the mechanical behavior andenergy absorption of thin-walled tubesrdquo Materials amp Designvol 32 no 6 pp 3594ndash3607 2011

[10] X Chang L Fu H-B Zhao and Y-B Zhang ldquoBehaviors ofaxially loaded circular concrete-filled steel tube (CFT) stubcolumns with notch in steel tubesrdquo 6in-Walled Structuresvol 73 no 12 pp 273ndash280 2013

[11] F-X Ding L Fu and Z-W Yu ldquoBehaviors of axially loadedsquare concrete-filled steel tube (CFST) Stub columns withnotch in steel tuberdquo 6in-Walled Structures vol 115 no 6pp 196ndash204 2017

[12] Y Liu and B Young ldquoBuckling of stainless steel square hollowsection compression membersrdquo Journal of ConstructionalSteel Research vol 59 no 2 pp 165ndash177 2003

[13] Z-P Chen Y-L Chen and M Zhong ldquoExperimental studyon axial compression capacity of concrete-filled square steeltubular columns with opening hole damagerdquo BuildingStructure vol 44 no 9 pp 9ndash14 2014 in Chinese

[14] Z-P Chen Y-L Chen andM Zhon ldquoExperimental study onmechanical properties of concrete-filled opening hole dam-aged steel tubular membersrdquo Industrial Construction vol 43no 2 pp 121ndash127 2013

[15] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof octagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 453ndash461 2016

[16] W Xu L-H Han and W Li ldquoPerformance of hexagonalCFST members under axial compression and bendingrdquoJournal of Constructional Steel Research vol 24 no 3pp 309ndash322 2017

[17] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof hexagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 502ndash513 2016

[18] M F Hassanein V I Patel and M Bock ldquoBehaviour anddesign of hexagonal concrete-filled steel tubular short col-umns under axial compressionrdquo Engineering Structuresvol 153 no 12 pp 732ndash748 2017

[19] B Evirgen A Tuncan and K Taskin ldquoStructural behavior ofconcrete filled steel tubular sections (CFTCFSt) under axialcompressionrdquo 6in-Walled Structures vol 80 no 7pp 46ndash56 2014

Advances in Civil Engineering 9

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Submit your manuscripts atwwwhindawicom

CFST stub columns 0e notch lengths are 30 60 and100mm A long notch length leads to weak restraint effectand low ultimate strength of the specimen

In the horizontally notched specimens the carryingcapacities of the specimens with a notch length of 30mm are21 and 53 larger than those of specimens with notchlengths of 60 and 100mm respectively In the verticallynotched specimens the carrying capacities of specimenswith a notch length of 30mm are 22 and 48 larger thanthose of specimens with notch lengths of 60 and 100mmrespectively

32 Influence of Notch Location Figure 8 illustrates the ef-fects of slotting location on the mechanical performance ofhexagonal CFSTstub columns0e notches are located at thesideway and corner Given the weak overall mechanical

behavior of steel pipe and concrete in the corner the ulti-mate strength of the CFST column notched in the corner issmaller than that in the sideway In the horizontally notchedspecimens the carrying capacities of the specimens with asideway notch are 16 larger than those of specimens with avertical notch In the vertically notched specimens thecarrying capacity of the specimen with a sideway notch is24 larger than those of specimens with a corner notch

33 InfluenceofNotchDirection Figure 9 presents the effectsof slotting orientation on the work performance of hexag-onal CFST stub columns 0e notch orientations includehorizontal and vertical Given the weak overall mechanicalbehavior of steel pipe and concrete in the corner the ulti-mate bearing capacity of the corner-notched specimens issmaller than that in the middle one For sideway-notched

Displacementtransducer

N

N

(a) (b)

Figure 3 Sketch for testing the apparatus of CFST stub column (a) Test setup (b) Loading device

Notch

(a)

Notch

(b)

Notch

(c)

Notch

(d)

Figure 4 Failure modes for hexagonal CFSTcolumns (a) Horizontal notch in the sideway (b) Notch in the corner (c) Vertical notch in thesideway (d) Vertical notch in the corner

4 Advances in Civil Engineering

Concretefailure

(a)

Concretefailure

(b)

Concretefailure

(c)

Concretefailure

(d)

Figure 5 Core-concrete damage of typical specimens (a) Horizontal slotting in the sideway (b) Horizontal slotting in the corner (c)Vertical slotting in the sideway (d) Vertical slotting in the corner

0 4 8 12 16 200

450

900

1350

1800

HCFT1HCFT2

HCFT3 HCFT-14

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(a)

HCFT4HCFT5

HCFT6 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(b)

HCFT7HCFT8

HCFT9 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(c)

HCFT10HCFT11

HCFT12 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(d)

Figure 6 Load-displacement curve of hexagonal CFST columns (a) HCFT1simHCFT3 (b) HCFT4simHCFT6 (c) HCFT1simHCFT3 (d)HCFT4simHCFT6

Advances in Civil Engineering 5

specimens the carrying capacity of the specimens with avertical notch is 20 larger than that of specimens with ahorizontal notch For corner-notched specimens the car-rying capacity of specimens with a vertical notch is 13larger than that of specimens with a horizontal notch

4 Calculation of the Ultimate BearingCapacity of Notched CFST Columns

41 Bearing Strength Ding et al [17] proposed equation (1)to estimate the ultimate strength of notched hexagonal CFSTcolumns

N fcAc(1 + KΦ) (1)

where Ac and As are the section area of concrete and steeltube respectively fc is the compressive strength of concrete

fcu is the strength of standard cube concrete fs is the yieldstrength of steel tube Φ is a confinement index and K is acoefficient (K 13)

According to equation (1) the calculated ultimatebearing capacity of HCFT13 or HCFT13 is 1555 kN and theratio of measured to calculated values is 1016 0e resultsshow that equation (1) can predict the ultimate strength ofhexagonal CFST columns well 0e equation was then ap-plied as the basic computational formula for the ultimatestrength of the notched specimens

0e slotting length slotting orientation and slottinglocation considerably affect the ultimate strength 0ereforethe ultimate strength of notched CFST columns can beexpressed as

N fcAc 1 + K1Φ( 1113857 (2)

0 30 60 90 120600

900

1200

1500

1800

HCFT1~3HCFT4~6

Notch length

Axi

al lo

ad N

(kN

)

(a)

HCFT7~9HCFT10~12

0 30 60 90 120600

900

1200

1500

1800

Notch length

Axi

al lo

ad N

(kN

)

(b)

Figure 7 Influence of notch length on the ultimate strength of specimens (a) Horizontal notch (HCFT1simHCFT6) (b) Vertical notch(HCFT7simHCFT12)

0 1 2 3

Corner

HCFT1 HCFT4HCFT2 HCFT5HCFT3 HCFT6

Sideway

Notch location

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(a)

HCFT7 HCFT10HCFT8 HCFT11HCFT9 HCFT12

CornerSideway

0 1 2 3Notch location

600

900

1200

1500

1800A

xial

load

N (k

N)

(b)

Figure 8 Influence of notch location on the ultimate strength of specimens (a) Horizontal notch (HCFT1simHCFT6) (b) Vertical notch(HCFT7simHCFT12)

6 Advances in Civil Engineering

where K1 is the reduction factor which can be expressed as

K1 13 minus 06β1 + 02β2( 1113857β3 (3)

where β1 β2 and β3 are parameters related to slotting lengthslotting orientation and slotting location respectively andexpressed as

β1

l

S horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β2

b

H horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β3

13 sideway

1 corner

⎧⎪⎨

⎪⎩

(4)

where S which is the outer girth of square steel pipe is equalto 6D

Table 2 shows the calculated and experimental results forall the specimens Nt and Nc are the test strength andcalculated strength respectively 0e average NtNc ratio is1004 with a coefficient of variation of 0018 for springelement Hence equation (2) is acceptable

42 Confining Effect 0e notched steel pipe cannot exertsufficient restraint effect on the core concrete 0is structurealso has poor mechanical properties 0us estimating therestraint effect becomes essential 0e ultimate strength ofCSFT is the total of the contribution of the core concrete and

steel pipe and the composite effect between the core concreteand steel pipe It can be expressed as

N Asfs + Acfc + Fs (5)

where Fs is the composite effect between the core concreteand steel pipe

For notched columns only a part of the steel pipe cancarry the compression 0us the ultimate strength for anotched specimen can be defined as follows

Nc Asefs + Acfc + Fs (6)

For horizontal slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus l minus 2t)t + 2 Dt (7)

For vertical slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus b minus 2t)t + 2 Dt (8)

Hence a confinement factor defined in equation (9) wasapplied to estimate the restraint effect of a notched steel pipeon the core concrete

λ Fs

Nc (9)

Table 2 shows the confinement factor for all the notchedspecimens 0e results show the following (1) 0e con-finement factor of the horizontally notched specimen isgreater than that of the vertically notched specimen (2) 0econfinement factor of the sideway-notched specimen issmaller than the corner-notched ones (3) For horizontallynotched specimen the longer the slotting the greater is theconfinement factor In the vertically notched specimen theconfinement factor decreases when the duration of slottingincreases

HCFT1 HCFT7HCFT2 HCFT8HCFT3 HCFT9

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(a)

HCFT4 HCFT10HCFT5 HCFT11HCFT6 HCFT12

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(b)

Figure 9 Influence of notch orientation on the ultimate strength of specimens (a) Sideway notch (HCFT1simHCFT6) (b) Corner notch(HCFT7simHCFT12)

Advances in Civil Engineering 7

5 Conclusions

Fourteen CFST stub columns were included in the ex-periments and notch length notch location and notchdirection were considered 0e effects of the structure-failure pattern were further investigated and load-dis-placement curves were obtained Finally a method forcalculating the ultimate strength of notched hexagonalCFSTcolumns was established0emain conclusions are asfollows

(1) Compared with undamaged CFST columns undercompression the specimens showed failure modesthat differ according to the slotting orientation Forhorizontally notched specimens the notch is closedunder axial loading For vertically notched ones theslotting shows outward buckling phenomenon

(2) 0e ultimate strength of notched CFST columns isless than that of intact CFST because the notchedsteel pipe cannot provide sufficient restraint on thecore concrete For notched hexagonal CFSTcolumnthe ultimate strength is less than those of undamagedones 0e experimental study illustrates that slottinglength slotting orientation and slotting locationconsiderably affect the ultimate strength of notchedCFST columns

(3) A formula proposed by Ding et al [17] was used toestimate the ultimate strength of undamaged hex-agonal CFST columns On this basis we establish anequation to predict the ultimate strength of notchedhexagonal CFSTcolumns 0e calculation results areconsistent with the experimental data

Data Availability

All data used to support the findings of this study are in-cluded within the article 0ere are not any restrictions ondata access

Conflicts of Interest

0e authors declare that they have no conflicts of interest

Acknowledgments

0is research work was financially supported by the HunanEducation Department Foundation Funded Project Grantnos 18B438 and 14C0217 the Project funded by ChinaPostdoctoral Science Foundation Grant no 2018M632990 theNatural Science Foundation of Hunan Province China Grantnos 2018JJ3021 2018JJ2525 and 2019JJ20029 the NationalKey Research Program of China Grant no 2017YFC0703404and the National Natural Science Foundation of China Grantno 51308548

References

[1] L-H Han C Hou and Q-L Wang ldquoSquare concrete filledsteel tubular (CFST) members under loading and chloridecorrosion Experimentsrdquo Journal of Constructional Steel Re-search vol 71 no 4 pp 11ndash25 2012

[2] X Zhou G Cheng J Liu D Gan and Y Frank ChenldquoBehavior of circular tubed-RC column to RC beam con-nections under axial compressionrdquo Journal of ConstructionalSteel Research vol 130 no 3 pp 96ndash108 2017

[3] C Tian C Xiao T Chen and X Fu ldquoExperimental study onthrough-beam connection system for concrete filled steel tubecolumn-RC beamrdquo Steel and Composite Structures vol 16no 2 pp 187ndash201 2014

[4] J Pan PWang Y Zheng ZWang and D Liu ldquoAn analyticalstudy of square CFTcolumns in bracing connection subjectedto axial loadingrdquo Advances in Civil Engineering vol 2018Article ID 8618937 15 pages 2018

[5] R Montuori and V Piluso ldquoAnalysis and modelling of CFTmembers moment curvature analysisrdquo 6in-Walled Struc-tures vol 86 no 1 pp 157ndash166 2015

[6] A A Nia K F Nejad H Badnava and H R FarhoudildquoEffects of buckling initiators on mechanical behavior of thin-walled square tubes subjected to oblique loadingrdquo 6in-Walled Structures vol 59 no 11 pp 87ndash96 2012

[7] Z Sadovsky J Krivacek V Ivanco and A DuricovaldquoComputational modelling of geometric imperfections andbuckling strength of cold-formed steelrdquo Journal of Con-structional Steel Research vol 78 no 12 pp 1ndash7 2012

[8] X-W Zhang H Su and T-X Yu ldquoEnergy absorption of anaxially crushed square tube with a buckling initiatorrdquo In-ternational Journal of Impact Engineering vol 36 no 3pp 402ndash417 2009

Table 2 Confinement factor for all the notched specimens

No Ase (mm2) Ac (mm2) fs (MPa) fc (MPa) Nc (kN) Fs (kN) λ

HCFT1 2000 25980 270 274 1468 215 0147HCFT2 2160 25980 270 274 1502 206 0137HCFT3 2280 25980 270 274 1527 199 0130HCFT4 2000 25980 270 274 1488 235 0158HCFT5 2160 25980 270 274 1514 218 0144HCFT6 2280 25980 270 274 1534 205 0134HCFT7 2360 25980 270 274 1519 169 0111HCFT8 2360 25980 270 274 1530 180 0118HCFT9 2360 25980 270 274 1539 188 0122HCFT10 2360 25980 270 274 1527 177 0116HCFT11 2360 25980 270 274 1536 186 0121HCFT12 2360 25980 270 274 1542 192 0125HCFT13 2400 25980 270 274 1555 194 0125HCFT14 2400 25980 270 274 1555 194 0125

8 Advances in Civil Engineering

[9] A A Nia H Badnava and K F Nejad ldquoAn experimentalinvestigation on crack effect on the mechanical behavior andenergy absorption of thin-walled tubesrdquo Materials amp Designvol 32 no 6 pp 3594ndash3607 2011

[10] X Chang L Fu H-B Zhao and Y-B Zhang ldquoBehaviors ofaxially loaded circular concrete-filled steel tube (CFT) stubcolumns with notch in steel tubesrdquo 6in-Walled Structuresvol 73 no 12 pp 273ndash280 2013

[11] F-X Ding L Fu and Z-W Yu ldquoBehaviors of axially loadedsquare concrete-filled steel tube (CFST) Stub columns withnotch in steel tuberdquo 6in-Walled Structures vol 115 no 6pp 196ndash204 2017

[12] Y Liu and B Young ldquoBuckling of stainless steel square hollowsection compression membersrdquo Journal of ConstructionalSteel Research vol 59 no 2 pp 165ndash177 2003

[13] Z-P Chen Y-L Chen and M Zhong ldquoExperimental studyon axial compression capacity of concrete-filled square steeltubular columns with opening hole damagerdquo BuildingStructure vol 44 no 9 pp 9ndash14 2014 in Chinese

[14] Z-P Chen Y-L Chen andM Zhon ldquoExperimental study onmechanical properties of concrete-filled opening hole dam-aged steel tubular membersrdquo Industrial Construction vol 43no 2 pp 121ndash127 2013

[15] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof octagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 453ndash461 2016

[16] W Xu L-H Han and W Li ldquoPerformance of hexagonalCFST members under axial compression and bendingrdquoJournal of Constructional Steel Research vol 24 no 3pp 309ndash322 2017

[17] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof hexagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 502ndash513 2016

[18] M F Hassanein V I Patel and M Bock ldquoBehaviour anddesign of hexagonal concrete-filled steel tubular short col-umns under axial compressionrdquo Engineering Structuresvol 153 no 12 pp 732ndash748 2017

[19] B Evirgen A Tuncan and K Taskin ldquoStructural behavior ofconcrete filled steel tubular sections (CFTCFSt) under axialcompressionrdquo 6in-Walled Structures vol 80 no 7pp 46ndash56 2014

Advances in Civil Engineering 9

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

Concretefailure

(a)

Concretefailure

(b)

Concretefailure

(c)

Concretefailure

(d)

Figure 5 Core-concrete damage of typical specimens (a) Horizontal slotting in the sideway (b) Horizontal slotting in the corner (c)Vertical slotting in the sideway (d) Vertical slotting in the corner

0 4 8 12 16 200

450

900

1350

1800

HCFT1HCFT2

HCFT3 HCFT-14

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(a)

HCFT4HCFT5

HCFT6 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(b)

HCFT7HCFT8

HCFT9 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(c)

HCFT10HCFT11

HCFT12 HCFT-14

0 4 8 12 16 200

450

900

1350

1800

Axi

al lo

ad N

(kN

)

Axial displacement Δ (mm)

(d)

Figure 6 Load-displacement curve of hexagonal CFST columns (a) HCFT1simHCFT3 (b) HCFT4simHCFT6 (c) HCFT1simHCFT3 (d)HCFT4simHCFT6

Advances in Civil Engineering 5

specimens the carrying capacity of the specimens with avertical notch is 20 larger than that of specimens with ahorizontal notch For corner-notched specimens the car-rying capacity of specimens with a vertical notch is 13larger than that of specimens with a horizontal notch

4 Calculation of the Ultimate BearingCapacity of Notched CFST Columns

41 Bearing Strength Ding et al [17] proposed equation (1)to estimate the ultimate strength of notched hexagonal CFSTcolumns

N fcAc(1 + KΦ) (1)

where Ac and As are the section area of concrete and steeltube respectively fc is the compressive strength of concrete

fcu is the strength of standard cube concrete fs is the yieldstrength of steel tube Φ is a confinement index and K is acoefficient (K 13)

According to equation (1) the calculated ultimatebearing capacity of HCFT13 or HCFT13 is 1555 kN and theratio of measured to calculated values is 1016 0e resultsshow that equation (1) can predict the ultimate strength ofhexagonal CFST columns well 0e equation was then ap-plied as the basic computational formula for the ultimatestrength of the notched specimens

0e slotting length slotting orientation and slottinglocation considerably affect the ultimate strength 0ereforethe ultimate strength of notched CFST columns can beexpressed as

N fcAc 1 + K1Φ( 1113857 (2)

0 30 60 90 120600

900

1200

1500

1800

HCFT1~3HCFT4~6

Notch length

Axi

al lo

ad N

(kN

)

(a)

HCFT7~9HCFT10~12

0 30 60 90 120600

900

1200

1500

1800

Notch length

Axi

al lo

ad N

(kN

)

(b)

Figure 7 Influence of notch length on the ultimate strength of specimens (a) Horizontal notch (HCFT1simHCFT6) (b) Vertical notch(HCFT7simHCFT12)

0 1 2 3

Corner

HCFT1 HCFT4HCFT2 HCFT5HCFT3 HCFT6

Sideway

Notch location

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(a)

HCFT7 HCFT10HCFT8 HCFT11HCFT9 HCFT12

CornerSideway

0 1 2 3Notch location

600

900

1200

1500

1800A

xial

load

N (k

N)

(b)

Figure 8 Influence of notch location on the ultimate strength of specimens (a) Horizontal notch (HCFT1simHCFT6) (b) Vertical notch(HCFT7simHCFT12)

6 Advances in Civil Engineering

where K1 is the reduction factor which can be expressed as

K1 13 minus 06β1 + 02β2( 1113857β3 (3)

where β1 β2 and β3 are parameters related to slotting lengthslotting orientation and slotting location respectively andexpressed as

β1

l

S horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β2

b

H horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β3

13 sideway

1 corner

⎧⎪⎨

⎪⎩

(4)

where S which is the outer girth of square steel pipe is equalto 6D

Table 2 shows the calculated and experimental results forall the specimens Nt and Nc are the test strength andcalculated strength respectively 0e average NtNc ratio is1004 with a coefficient of variation of 0018 for springelement Hence equation (2) is acceptable

42 Confining Effect 0e notched steel pipe cannot exertsufficient restraint effect on the core concrete 0is structurealso has poor mechanical properties 0us estimating therestraint effect becomes essential 0e ultimate strength ofCSFT is the total of the contribution of the core concrete and

steel pipe and the composite effect between the core concreteand steel pipe It can be expressed as

N Asfs + Acfc + Fs (5)

where Fs is the composite effect between the core concreteand steel pipe

For notched columns only a part of the steel pipe cancarry the compression 0us the ultimate strength for anotched specimen can be defined as follows

Nc Asefs + Acfc + Fs (6)

For horizontal slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus l minus 2t)t + 2 Dt (7)

For vertical slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus b minus 2t)t + 2 Dt (8)

Hence a confinement factor defined in equation (9) wasapplied to estimate the restraint effect of a notched steel pipeon the core concrete

λ Fs

Nc (9)

Table 2 shows the confinement factor for all the notchedspecimens 0e results show the following (1) 0e con-finement factor of the horizontally notched specimen isgreater than that of the vertically notched specimen (2) 0econfinement factor of the sideway-notched specimen issmaller than the corner-notched ones (3) For horizontallynotched specimen the longer the slotting the greater is theconfinement factor In the vertically notched specimen theconfinement factor decreases when the duration of slottingincreases

HCFT1 HCFT7HCFT2 HCFT8HCFT3 HCFT9

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(a)

HCFT4 HCFT10HCFT5 HCFT11HCFT6 HCFT12

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(b)

Figure 9 Influence of notch orientation on the ultimate strength of specimens (a) Sideway notch (HCFT1simHCFT6) (b) Corner notch(HCFT7simHCFT12)

Advances in Civil Engineering 7

5 Conclusions

Fourteen CFST stub columns were included in the ex-periments and notch length notch location and notchdirection were considered 0e effects of the structure-failure pattern were further investigated and load-dis-placement curves were obtained Finally a method forcalculating the ultimate strength of notched hexagonalCFSTcolumns was established0emain conclusions are asfollows

(1) Compared with undamaged CFST columns undercompression the specimens showed failure modesthat differ according to the slotting orientation Forhorizontally notched specimens the notch is closedunder axial loading For vertically notched ones theslotting shows outward buckling phenomenon

(2) 0e ultimate strength of notched CFST columns isless than that of intact CFST because the notchedsteel pipe cannot provide sufficient restraint on thecore concrete For notched hexagonal CFSTcolumnthe ultimate strength is less than those of undamagedones 0e experimental study illustrates that slottinglength slotting orientation and slotting locationconsiderably affect the ultimate strength of notchedCFST columns

(3) A formula proposed by Ding et al [17] was used toestimate the ultimate strength of undamaged hex-agonal CFST columns On this basis we establish anequation to predict the ultimate strength of notchedhexagonal CFSTcolumns 0e calculation results areconsistent with the experimental data

Data Availability

All data used to support the findings of this study are in-cluded within the article 0ere are not any restrictions ondata access

Conflicts of Interest

0e authors declare that they have no conflicts of interest

Acknowledgments

0is research work was financially supported by the HunanEducation Department Foundation Funded Project Grantnos 18B438 and 14C0217 the Project funded by ChinaPostdoctoral Science Foundation Grant no 2018M632990 theNatural Science Foundation of Hunan Province China Grantnos 2018JJ3021 2018JJ2525 and 2019JJ20029 the NationalKey Research Program of China Grant no 2017YFC0703404and the National Natural Science Foundation of China Grantno 51308548

References

[1] L-H Han C Hou and Q-L Wang ldquoSquare concrete filledsteel tubular (CFST) members under loading and chloridecorrosion Experimentsrdquo Journal of Constructional Steel Re-search vol 71 no 4 pp 11ndash25 2012

[2] X Zhou G Cheng J Liu D Gan and Y Frank ChenldquoBehavior of circular tubed-RC column to RC beam con-nections under axial compressionrdquo Journal of ConstructionalSteel Research vol 130 no 3 pp 96ndash108 2017

[3] C Tian C Xiao T Chen and X Fu ldquoExperimental study onthrough-beam connection system for concrete filled steel tubecolumn-RC beamrdquo Steel and Composite Structures vol 16no 2 pp 187ndash201 2014

[4] J Pan PWang Y Zheng ZWang and D Liu ldquoAn analyticalstudy of square CFTcolumns in bracing connection subjectedto axial loadingrdquo Advances in Civil Engineering vol 2018Article ID 8618937 15 pages 2018

[5] R Montuori and V Piluso ldquoAnalysis and modelling of CFTmembers moment curvature analysisrdquo 6in-Walled Struc-tures vol 86 no 1 pp 157ndash166 2015

[6] A A Nia K F Nejad H Badnava and H R FarhoudildquoEffects of buckling initiators on mechanical behavior of thin-walled square tubes subjected to oblique loadingrdquo 6in-Walled Structures vol 59 no 11 pp 87ndash96 2012

[7] Z Sadovsky J Krivacek V Ivanco and A DuricovaldquoComputational modelling of geometric imperfections andbuckling strength of cold-formed steelrdquo Journal of Con-structional Steel Research vol 78 no 12 pp 1ndash7 2012

[8] X-W Zhang H Su and T-X Yu ldquoEnergy absorption of anaxially crushed square tube with a buckling initiatorrdquo In-ternational Journal of Impact Engineering vol 36 no 3pp 402ndash417 2009

Table 2 Confinement factor for all the notched specimens

No Ase (mm2) Ac (mm2) fs (MPa) fc (MPa) Nc (kN) Fs (kN) λ

HCFT1 2000 25980 270 274 1468 215 0147HCFT2 2160 25980 270 274 1502 206 0137HCFT3 2280 25980 270 274 1527 199 0130HCFT4 2000 25980 270 274 1488 235 0158HCFT5 2160 25980 270 274 1514 218 0144HCFT6 2280 25980 270 274 1534 205 0134HCFT7 2360 25980 270 274 1519 169 0111HCFT8 2360 25980 270 274 1530 180 0118HCFT9 2360 25980 270 274 1539 188 0122HCFT10 2360 25980 270 274 1527 177 0116HCFT11 2360 25980 270 274 1536 186 0121HCFT12 2360 25980 270 274 1542 192 0125HCFT13 2400 25980 270 274 1555 194 0125HCFT14 2400 25980 270 274 1555 194 0125

8 Advances in Civil Engineering

[9] A A Nia H Badnava and K F Nejad ldquoAn experimentalinvestigation on crack effect on the mechanical behavior andenergy absorption of thin-walled tubesrdquo Materials amp Designvol 32 no 6 pp 3594ndash3607 2011

[10] X Chang L Fu H-B Zhao and Y-B Zhang ldquoBehaviors ofaxially loaded circular concrete-filled steel tube (CFT) stubcolumns with notch in steel tubesrdquo 6in-Walled Structuresvol 73 no 12 pp 273ndash280 2013

[11] F-X Ding L Fu and Z-W Yu ldquoBehaviors of axially loadedsquare concrete-filled steel tube (CFST) Stub columns withnotch in steel tuberdquo 6in-Walled Structures vol 115 no 6pp 196ndash204 2017

[12] Y Liu and B Young ldquoBuckling of stainless steel square hollowsection compression membersrdquo Journal of ConstructionalSteel Research vol 59 no 2 pp 165ndash177 2003

[13] Z-P Chen Y-L Chen and M Zhong ldquoExperimental studyon axial compression capacity of concrete-filled square steeltubular columns with opening hole damagerdquo BuildingStructure vol 44 no 9 pp 9ndash14 2014 in Chinese

[14] Z-P Chen Y-L Chen andM Zhon ldquoExperimental study onmechanical properties of concrete-filled opening hole dam-aged steel tubular membersrdquo Industrial Construction vol 43no 2 pp 121ndash127 2013

[15] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof octagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 453ndash461 2016

[16] W Xu L-H Han and W Li ldquoPerformance of hexagonalCFST members under axial compression and bendingrdquoJournal of Constructional Steel Research vol 24 no 3pp 309ndash322 2017

[17] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof hexagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 502ndash513 2016

[18] M F Hassanein V I Patel and M Bock ldquoBehaviour anddesign of hexagonal concrete-filled steel tubular short col-umns under axial compressionrdquo Engineering Structuresvol 153 no 12 pp 732ndash748 2017

[19] B Evirgen A Tuncan and K Taskin ldquoStructural behavior ofconcrete filled steel tubular sections (CFTCFSt) under axialcompressionrdquo 6in-Walled Structures vol 80 no 7pp 46ndash56 2014

Advances in Civil Engineering 9

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

specimens the carrying capacity of the specimens with avertical notch is 20 larger than that of specimens with ahorizontal notch For corner-notched specimens the car-rying capacity of specimens with a vertical notch is 13larger than that of specimens with a horizontal notch

4 Calculation of the Ultimate BearingCapacity of Notched CFST Columns

41 Bearing Strength Ding et al [17] proposed equation (1)to estimate the ultimate strength of notched hexagonal CFSTcolumns

N fcAc(1 + KΦ) (1)

where Ac and As are the section area of concrete and steeltube respectively fc is the compressive strength of concrete

fcu is the strength of standard cube concrete fs is the yieldstrength of steel tube Φ is a confinement index and K is acoefficient (K 13)

According to equation (1) the calculated ultimatebearing capacity of HCFT13 or HCFT13 is 1555 kN and theratio of measured to calculated values is 1016 0e resultsshow that equation (1) can predict the ultimate strength ofhexagonal CFST columns well 0e equation was then ap-plied as the basic computational formula for the ultimatestrength of the notched specimens

0e slotting length slotting orientation and slottinglocation considerably affect the ultimate strength 0ereforethe ultimate strength of notched CFST columns can beexpressed as

N fcAc 1 + K1Φ( 1113857 (2)

0 30 60 90 120600

900

1200

1500

1800

HCFT1~3HCFT4~6

Notch length

Axi

al lo

ad N

(kN

)

(a)

HCFT7~9HCFT10~12

0 30 60 90 120600

900

1200

1500

1800

Notch length

Axi

al lo

ad N

(kN

)

(b)

Figure 7 Influence of notch length on the ultimate strength of specimens (a) Horizontal notch (HCFT1simHCFT6) (b) Vertical notch(HCFT7simHCFT12)

0 1 2 3

Corner

HCFT1 HCFT4HCFT2 HCFT5HCFT3 HCFT6

Sideway

Notch location

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(a)

HCFT7 HCFT10HCFT8 HCFT11HCFT9 HCFT12

CornerSideway

0 1 2 3Notch location

600

900

1200

1500

1800A

xial

load

N (k

N)

(b)

Figure 8 Influence of notch location on the ultimate strength of specimens (a) Horizontal notch (HCFT1simHCFT6) (b) Vertical notch(HCFT7simHCFT12)

6 Advances in Civil Engineering

where K1 is the reduction factor which can be expressed as

K1 13 minus 06β1 + 02β2( 1113857β3 (3)

where β1 β2 and β3 are parameters related to slotting lengthslotting orientation and slotting location respectively andexpressed as

β1

l

S horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β2

b

H horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β3

13 sideway

1 corner

⎧⎪⎨

⎪⎩

(4)

where S which is the outer girth of square steel pipe is equalto 6D

Table 2 shows the calculated and experimental results forall the specimens Nt and Nc are the test strength andcalculated strength respectively 0e average NtNc ratio is1004 with a coefficient of variation of 0018 for springelement Hence equation (2) is acceptable

42 Confining Effect 0e notched steel pipe cannot exertsufficient restraint effect on the core concrete 0is structurealso has poor mechanical properties 0us estimating therestraint effect becomes essential 0e ultimate strength ofCSFT is the total of the contribution of the core concrete and

steel pipe and the composite effect between the core concreteand steel pipe It can be expressed as

N Asfs + Acfc + Fs (5)

where Fs is the composite effect between the core concreteand steel pipe

For notched columns only a part of the steel pipe cancarry the compression 0us the ultimate strength for anotched specimen can be defined as follows

Nc Asefs + Acfc + Fs (6)

For horizontal slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus l minus 2t)t + 2 Dt (7)

For vertical slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus b minus 2t)t + 2 Dt (8)

Hence a confinement factor defined in equation (9) wasapplied to estimate the restraint effect of a notched steel pipeon the core concrete

λ Fs

Nc (9)

Table 2 shows the confinement factor for all the notchedspecimens 0e results show the following (1) 0e con-finement factor of the horizontally notched specimen isgreater than that of the vertically notched specimen (2) 0econfinement factor of the sideway-notched specimen issmaller than the corner-notched ones (3) For horizontallynotched specimen the longer the slotting the greater is theconfinement factor In the vertically notched specimen theconfinement factor decreases when the duration of slottingincreases

HCFT1 HCFT7HCFT2 HCFT8HCFT3 HCFT9

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(a)

HCFT4 HCFT10HCFT5 HCFT11HCFT6 HCFT12

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(b)

Figure 9 Influence of notch orientation on the ultimate strength of specimens (a) Sideway notch (HCFT1simHCFT6) (b) Corner notch(HCFT7simHCFT12)

Advances in Civil Engineering 7

5 Conclusions

Fourteen CFST stub columns were included in the ex-periments and notch length notch location and notchdirection were considered 0e effects of the structure-failure pattern were further investigated and load-dis-placement curves were obtained Finally a method forcalculating the ultimate strength of notched hexagonalCFSTcolumns was established0emain conclusions are asfollows

(1) Compared with undamaged CFST columns undercompression the specimens showed failure modesthat differ according to the slotting orientation Forhorizontally notched specimens the notch is closedunder axial loading For vertically notched ones theslotting shows outward buckling phenomenon

(2) 0e ultimate strength of notched CFST columns isless than that of intact CFST because the notchedsteel pipe cannot provide sufficient restraint on thecore concrete For notched hexagonal CFSTcolumnthe ultimate strength is less than those of undamagedones 0e experimental study illustrates that slottinglength slotting orientation and slotting locationconsiderably affect the ultimate strength of notchedCFST columns

(3) A formula proposed by Ding et al [17] was used toestimate the ultimate strength of undamaged hex-agonal CFST columns On this basis we establish anequation to predict the ultimate strength of notchedhexagonal CFSTcolumns 0e calculation results areconsistent with the experimental data

Data Availability

All data used to support the findings of this study are in-cluded within the article 0ere are not any restrictions ondata access

Conflicts of Interest

0e authors declare that they have no conflicts of interest

Acknowledgments

0is research work was financially supported by the HunanEducation Department Foundation Funded Project Grantnos 18B438 and 14C0217 the Project funded by ChinaPostdoctoral Science Foundation Grant no 2018M632990 theNatural Science Foundation of Hunan Province China Grantnos 2018JJ3021 2018JJ2525 and 2019JJ20029 the NationalKey Research Program of China Grant no 2017YFC0703404and the National Natural Science Foundation of China Grantno 51308548

References

[1] L-H Han C Hou and Q-L Wang ldquoSquare concrete filledsteel tubular (CFST) members under loading and chloridecorrosion Experimentsrdquo Journal of Constructional Steel Re-search vol 71 no 4 pp 11ndash25 2012

[2] X Zhou G Cheng J Liu D Gan and Y Frank ChenldquoBehavior of circular tubed-RC column to RC beam con-nections under axial compressionrdquo Journal of ConstructionalSteel Research vol 130 no 3 pp 96ndash108 2017

[3] C Tian C Xiao T Chen and X Fu ldquoExperimental study onthrough-beam connection system for concrete filled steel tubecolumn-RC beamrdquo Steel and Composite Structures vol 16no 2 pp 187ndash201 2014

[4] J Pan PWang Y Zheng ZWang and D Liu ldquoAn analyticalstudy of square CFTcolumns in bracing connection subjectedto axial loadingrdquo Advances in Civil Engineering vol 2018Article ID 8618937 15 pages 2018

[5] R Montuori and V Piluso ldquoAnalysis and modelling of CFTmembers moment curvature analysisrdquo 6in-Walled Struc-tures vol 86 no 1 pp 157ndash166 2015

[6] A A Nia K F Nejad H Badnava and H R FarhoudildquoEffects of buckling initiators on mechanical behavior of thin-walled square tubes subjected to oblique loadingrdquo 6in-Walled Structures vol 59 no 11 pp 87ndash96 2012

[7] Z Sadovsky J Krivacek V Ivanco and A DuricovaldquoComputational modelling of geometric imperfections andbuckling strength of cold-formed steelrdquo Journal of Con-structional Steel Research vol 78 no 12 pp 1ndash7 2012

[8] X-W Zhang H Su and T-X Yu ldquoEnergy absorption of anaxially crushed square tube with a buckling initiatorrdquo In-ternational Journal of Impact Engineering vol 36 no 3pp 402ndash417 2009

Table 2 Confinement factor for all the notched specimens

No Ase (mm2) Ac (mm2) fs (MPa) fc (MPa) Nc (kN) Fs (kN) λ

HCFT1 2000 25980 270 274 1468 215 0147HCFT2 2160 25980 270 274 1502 206 0137HCFT3 2280 25980 270 274 1527 199 0130HCFT4 2000 25980 270 274 1488 235 0158HCFT5 2160 25980 270 274 1514 218 0144HCFT6 2280 25980 270 274 1534 205 0134HCFT7 2360 25980 270 274 1519 169 0111HCFT8 2360 25980 270 274 1530 180 0118HCFT9 2360 25980 270 274 1539 188 0122HCFT10 2360 25980 270 274 1527 177 0116HCFT11 2360 25980 270 274 1536 186 0121HCFT12 2360 25980 270 274 1542 192 0125HCFT13 2400 25980 270 274 1555 194 0125HCFT14 2400 25980 270 274 1555 194 0125

8 Advances in Civil Engineering

[9] A A Nia H Badnava and K F Nejad ldquoAn experimentalinvestigation on crack effect on the mechanical behavior andenergy absorption of thin-walled tubesrdquo Materials amp Designvol 32 no 6 pp 3594ndash3607 2011

[10] X Chang L Fu H-B Zhao and Y-B Zhang ldquoBehaviors ofaxially loaded circular concrete-filled steel tube (CFT) stubcolumns with notch in steel tubesrdquo 6in-Walled Structuresvol 73 no 12 pp 273ndash280 2013

[11] F-X Ding L Fu and Z-W Yu ldquoBehaviors of axially loadedsquare concrete-filled steel tube (CFST) Stub columns withnotch in steel tuberdquo 6in-Walled Structures vol 115 no 6pp 196ndash204 2017

[12] Y Liu and B Young ldquoBuckling of stainless steel square hollowsection compression membersrdquo Journal of ConstructionalSteel Research vol 59 no 2 pp 165ndash177 2003

[13] Z-P Chen Y-L Chen and M Zhong ldquoExperimental studyon axial compression capacity of concrete-filled square steeltubular columns with opening hole damagerdquo BuildingStructure vol 44 no 9 pp 9ndash14 2014 in Chinese

[14] Z-P Chen Y-L Chen andM Zhon ldquoExperimental study onmechanical properties of concrete-filled opening hole dam-aged steel tubular membersrdquo Industrial Construction vol 43no 2 pp 121ndash127 2013

[15] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof octagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 453ndash461 2016

[16] W Xu L-H Han and W Li ldquoPerformance of hexagonalCFST members under axial compression and bendingrdquoJournal of Constructional Steel Research vol 24 no 3pp 309ndash322 2017

[17] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof hexagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 502ndash513 2016

[18] M F Hassanein V I Patel and M Bock ldquoBehaviour anddesign of hexagonal concrete-filled steel tubular short col-umns under axial compressionrdquo Engineering Structuresvol 153 no 12 pp 732ndash748 2017

[19] B Evirgen A Tuncan and K Taskin ldquoStructural behavior ofconcrete filled steel tubular sections (CFTCFSt) under axialcompressionrdquo 6in-Walled Structures vol 80 no 7pp 46ndash56 2014

Advances in Civil Engineering 9

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

where K1 is the reduction factor which can be expressed as

K1 13 minus 06β1 + 02β2( 1113857β3 (3)

where β1 β2 and β3 are parameters related to slotting lengthslotting orientation and slotting location respectively andexpressed as

β1

l

S horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β2

b

H horizontal notch

b

S vertical notch

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

β3

13 sideway

1 corner

⎧⎪⎨

⎪⎩

(4)

where S which is the outer girth of square steel pipe is equalto 6D

Table 2 shows the calculated and experimental results forall the specimens Nt and Nc are the test strength andcalculated strength respectively 0e average NtNc ratio is1004 with a coefficient of variation of 0018 for springelement Hence equation (2) is acceptable

42 Confining Effect 0e notched steel pipe cannot exertsufficient restraint effect on the core concrete 0is structurealso has poor mechanical properties 0us estimating therestraint effect becomes essential 0e ultimate strength ofCSFT is the total of the contribution of the core concrete and

steel pipe and the composite effect between the core concreteand steel pipe It can be expressed as

N Asfs + Acfc + Fs (5)

where Fs is the composite effect between the core concreteand steel pipe

For notched columns only a part of the steel pipe cancarry the compression 0us the ultimate strength for anotched specimen can be defined as follows

Nc Asefs + Acfc + Fs (6)

For horizontal slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus l minus 2t)t + 2 Dt (7)

For vertical slotting the effective area of the steel pipe(Ase) can be written as follows

Ase (D minus 2t)t +(D minus b minus 2t)t + 2 Dt (8)

Hence a confinement factor defined in equation (9) wasapplied to estimate the restraint effect of a notched steel pipeon the core concrete

λ Fs

Nc (9)

Table 2 shows the confinement factor for all the notchedspecimens 0e results show the following (1) 0e con-finement factor of the horizontally notched specimen isgreater than that of the vertically notched specimen (2) 0econfinement factor of the sideway-notched specimen issmaller than the corner-notched ones (3) For horizontallynotched specimen the longer the slotting the greater is theconfinement factor In the vertically notched specimen theconfinement factor decreases when the duration of slottingincreases

HCFT1 HCFT7HCFT2 HCFT8HCFT3 HCFT9

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(a)

HCFT4 HCFT10HCFT5 HCFT11HCFT6 HCFT12

VerticalHorizontal

0 1 2 3Notch orientation

600

900

1200

1500

1800

Axi

al lo

ad N

(kN

)

(b)

Figure 9 Influence of notch orientation on the ultimate strength of specimens (a) Sideway notch (HCFT1simHCFT6) (b) Corner notch(HCFT7simHCFT12)

Advances in Civil Engineering 7

5 Conclusions

Fourteen CFST stub columns were included in the ex-periments and notch length notch location and notchdirection were considered 0e effects of the structure-failure pattern were further investigated and load-dis-placement curves were obtained Finally a method forcalculating the ultimate strength of notched hexagonalCFSTcolumns was established0emain conclusions are asfollows

(1) Compared with undamaged CFST columns undercompression the specimens showed failure modesthat differ according to the slotting orientation Forhorizontally notched specimens the notch is closedunder axial loading For vertically notched ones theslotting shows outward buckling phenomenon

(2) 0e ultimate strength of notched CFST columns isless than that of intact CFST because the notchedsteel pipe cannot provide sufficient restraint on thecore concrete For notched hexagonal CFSTcolumnthe ultimate strength is less than those of undamagedones 0e experimental study illustrates that slottinglength slotting orientation and slotting locationconsiderably affect the ultimate strength of notchedCFST columns

(3) A formula proposed by Ding et al [17] was used toestimate the ultimate strength of undamaged hex-agonal CFST columns On this basis we establish anequation to predict the ultimate strength of notchedhexagonal CFSTcolumns 0e calculation results areconsistent with the experimental data

Data Availability

All data used to support the findings of this study are in-cluded within the article 0ere are not any restrictions ondata access

Conflicts of Interest

0e authors declare that they have no conflicts of interest

Acknowledgments

0is research work was financially supported by the HunanEducation Department Foundation Funded Project Grantnos 18B438 and 14C0217 the Project funded by ChinaPostdoctoral Science Foundation Grant no 2018M632990 theNatural Science Foundation of Hunan Province China Grantnos 2018JJ3021 2018JJ2525 and 2019JJ20029 the NationalKey Research Program of China Grant no 2017YFC0703404and the National Natural Science Foundation of China Grantno 51308548

References

[1] L-H Han C Hou and Q-L Wang ldquoSquare concrete filledsteel tubular (CFST) members under loading and chloridecorrosion Experimentsrdquo Journal of Constructional Steel Re-search vol 71 no 4 pp 11ndash25 2012

[2] X Zhou G Cheng J Liu D Gan and Y Frank ChenldquoBehavior of circular tubed-RC column to RC beam con-nections under axial compressionrdquo Journal of ConstructionalSteel Research vol 130 no 3 pp 96ndash108 2017

[3] C Tian C Xiao T Chen and X Fu ldquoExperimental study onthrough-beam connection system for concrete filled steel tubecolumn-RC beamrdquo Steel and Composite Structures vol 16no 2 pp 187ndash201 2014

[4] J Pan PWang Y Zheng ZWang and D Liu ldquoAn analyticalstudy of square CFTcolumns in bracing connection subjectedto axial loadingrdquo Advances in Civil Engineering vol 2018Article ID 8618937 15 pages 2018

[5] R Montuori and V Piluso ldquoAnalysis and modelling of CFTmembers moment curvature analysisrdquo 6in-Walled Struc-tures vol 86 no 1 pp 157ndash166 2015

[6] A A Nia K F Nejad H Badnava and H R FarhoudildquoEffects of buckling initiators on mechanical behavior of thin-walled square tubes subjected to oblique loadingrdquo 6in-Walled Structures vol 59 no 11 pp 87ndash96 2012

[7] Z Sadovsky J Krivacek V Ivanco and A DuricovaldquoComputational modelling of geometric imperfections andbuckling strength of cold-formed steelrdquo Journal of Con-structional Steel Research vol 78 no 12 pp 1ndash7 2012

[8] X-W Zhang H Su and T-X Yu ldquoEnergy absorption of anaxially crushed square tube with a buckling initiatorrdquo In-ternational Journal of Impact Engineering vol 36 no 3pp 402ndash417 2009

Table 2 Confinement factor for all the notched specimens

No Ase (mm2) Ac (mm2) fs (MPa) fc (MPa) Nc (kN) Fs (kN) λ

HCFT1 2000 25980 270 274 1468 215 0147HCFT2 2160 25980 270 274 1502 206 0137HCFT3 2280 25980 270 274 1527 199 0130HCFT4 2000 25980 270 274 1488 235 0158HCFT5 2160 25980 270 274 1514 218 0144HCFT6 2280 25980 270 274 1534 205 0134HCFT7 2360 25980 270 274 1519 169 0111HCFT8 2360 25980 270 274 1530 180 0118HCFT9 2360 25980 270 274 1539 188 0122HCFT10 2360 25980 270 274 1527 177 0116HCFT11 2360 25980 270 274 1536 186 0121HCFT12 2360 25980 270 274 1542 192 0125HCFT13 2400 25980 270 274 1555 194 0125HCFT14 2400 25980 270 274 1555 194 0125

8 Advances in Civil Engineering

[9] A A Nia H Badnava and K F Nejad ldquoAn experimentalinvestigation on crack effect on the mechanical behavior andenergy absorption of thin-walled tubesrdquo Materials amp Designvol 32 no 6 pp 3594ndash3607 2011

[10] X Chang L Fu H-B Zhao and Y-B Zhang ldquoBehaviors ofaxially loaded circular concrete-filled steel tube (CFT) stubcolumns with notch in steel tubesrdquo 6in-Walled Structuresvol 73 no 12 pp 273ndash280 2013

[11] F-X Ding L Fu and Z-W Yu ldquoBehaviors of axially loadedsquare concrete-filled steel tube (CFST) Stub columns withnotch in steel tuberdquo 6in-Walled Structures vol 115 no 6pp 196ndash204 2017

[12] Y Liu and B Young ldquoBuckling of stainless steel square hollowsection compression membersrdquo Journal of ConstructionalSteel Research vol 59 no 2 pp 165ndash177 2003

[13] Z-P Chen Y-L Chen and M Zhong ldquoExperimental studyon axial compression capacity of concrete-filled square steeltubular columns with opening hole damagerdquo BuildingStructure vol 44 no 9 pp 9ndash14 2014 in Chinese

[14] Z-P Chen Y-L Chen andM Zhon ldquoExperimental study onmechanical properties of concrete-filled opening hole dam-aged steel tubular membersrdquo Industrial Construction vol 43no 2 pp 121ndash127 2013

[15] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof octagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 453ndash461 2016

[16] W Xu L-H Han and W Li ldquoPerformance of hexagonalCFST members under axial compression and bendingrdquoJournal of Constructional Steel Research vol 24 no 3pp 309ndash322 2017

[17] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof hexagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 502ndash513 2016

[18] M F Hassanein V I Patel and M Bock ldquoBehaviour anddesign of hexagonal concrete-filled steel tubular short col-umns under axial compressionrdquo Engineering Structuresvol 153 no 12 pp 732ndash748 2017

[19] B Evirgen A Tuncan and K Taskin ldquoStructural behavior ofconcrete filled steel tubular sections (CFTCFSt) under axialcompressionrdquo 6in-Walled Structures vol 80 no 7pp 46ndash56 2014

Advances in Civil Engineering 9

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

5 Conclusions

Fourteen CFST stub columns were included in the ex-periments and notch length notch location and notchdirection were considered 0e effects of the structure-failure pattern were further investigated and load-dis-placement curves were obtained Finally a method forcalculating the ultimate strength of notched hexagonalCFSTcolumns was established0emain conclusions are asfollows

(1) Compared with undamaged CFST columns undercompression the specimens showed failure modesthat differ according to the slotting orientation Forhorizontally notched specimens the notch is closedunder axial loading For vertically notched ones theslotting shows outward buckling phenomenon

(2) 0e ultimate strength of notched CFST columns isless than that of intact CFST because the notchedsteel pipe cannot provide sufficient restraint on thecore concrete For notched hexagonal CFSTcolumnthe ultimate strength is less than those of undamagedones 0e experimental study illustrates that slottinglength slotting orientation and slotting locationconsiderably affect the ultimate strength of notchedCFST columns

(3) A formula proposed by Ding et al [17] was used toestimate the ultimate strength of undamaged hex-agonal CFST columns On this basis we establish anequation to predict the ultimate strength of notchedhexagonal CFSTcolumns 0e calculation results areconsistent with the experimental data

Data Availability

All data used to support the findings of this study are in-cluded within the article 0ere are not any restrictions ondata access

Conflicts of Interest

0e authors declare that they have no conflicts of interest

Acknowledgments

0is research work was financially supported by the HunanEducation Department Foundation Funded Project Grantnos 18B438 and 14C0217 the Project funded by ChinaPostdoctoral Science Foundation Grant no 2018M632990 theNatural Science Foundation of Hunan Province China Grantnos 2018JJ3021 2018JJ2525 and 2019JJ20029 the NationalKey Research Program of China Grant no 2017YFC0703404and the National Natural Science Foundation of China Grantno 51308548

References

[1] L-H Han C Hou and Q-L Wang ldquoSquare concrete filledsteel tubular (CFST) members under loading and chloridecorrosion Experimentsrdquo Journal of Constructional Steel Re-search vol 71 no 4 pp 11ndash25 2012

[2] X Zhou G Cheng J Liu D Gan and Y Frank ChenldquoBehavior of circular tubed-RC column to RC beam con-nections under axial compressionrdquo Journal of ConstructionalSteel Research vol 130 no 3 pp 96ndash108 2017

[3] C Tian C Xiao T Chen and X Fu ldquoExperimental study onthrough-beam connection system for concrete filled steel tubecolumn-RC beamrdquo Steel and Composite Structures vol 16no 2 pp 187ndash201 2014

[4] J Pan PWang Y Zheng ZWang and D Liu ldquoAn analyticalstudy of square CFTcolumns in bracing connection subjectedto axial loadingrdquo Advances in Civil Engineering vol 2018Article ID 8618937 15 pages 2018

[5] R Montuori and V Piluso ldquoAnalysis and modelling of CFTmembers moment curvature analysisrdquo 6in-Walled Struc-tures vol 86 no 1 pp 157ndash166 2015

[6] A A Nia K F Nejad H Badnava and H R FarhoudildquoEffects of buckling initiators on mechanical behavior of thin-walled square tubes subjected to oblique loadingrdquo 6in-Walled Structures vol 59 no 11 pp 87ndash96 2012

[7] Z Sadovsky J Krivacek V Ivanco and A DuricovaldquoComputational modelling of geometric imperfections andbuckling strength of cold-formed steelrdquo Journal of Con-structional Steel Research vol 78 no 12 pp 1ndash7 2012

[8] X-W Zhang H Su and T-X Yu ldquoEnergy absorption of anaxially crushed square tube with a buckling initiatorrdquo In-ternational Journal of Impact Engineering vol 36 no 3pp 402ndash417 2009

Table 2 Confinement factor for all the notched specimens

No Ase (mm2) Ac (mm2) fs (MPa) fc (MPa) Nc (kN) Fs (kN) λ

HCFT1 2000 25980 270 274 1468 215 0147HCFT2 2160 25980 270 274 1502 206 0137HCFT3 2280 25980 270 274 1527 199 0130HCFT4 2000 25980 270 274 1488 235 0158HCFT5 2160 25980 270 274 1514 218 0144HCFT6 2280 25980 270 274 1534 205 0134HCFT7 2360 25980 270 274 1519 169 0111HCFT8 2360 25980 270 274 1530 180 0118HCFT9 2360 25980 270 274 1539 188 0122HCFT10 2360 25980 270 274 1527 177 0116HCFT11 2360 25980 270 274 1536 186 0121HCFT12 2360 25980 270 274 1542 192 0125HCFT13 2400 25980 270 274 1555 194 0125HCFT14 2400 25980 270 274 1555 194 0125

8 Advances in Civil Engineering

[9] A A Nia H Badnava and K F Nejad ldquoAn experimentalinvestigation on crack effect on the mechanical behavior andenergy absorption of thin-walled tubesrdquo Materials amp Designvol 32 no 6 pp 3594ndash3607 2011

[10] X Chang L Fu H-B Zhao and Y-B Zhang ldquoBehaviors ofaxially loaded circular concrete-filled steel tube (CFT) stubcolumns with notch in steel tubesrdquo 6in-Walled Structuresvol 73 no 12 pp 273ndash280 2013

[11] F-X Ding L Fu and Z-W Yu ldquoBehaviors of axially loadedsquare concrete-filled steel tube (CFST) Stub columns withnotch in steel tuberdquo 6in-Walled Structures vol 115 no 6pp 196ndash204 2017

[12] Y Liu and B Young ldquoBuckling of stainless steel square hollowsection compression membersrdquo Journal of ConstructionalSteel Research vol 59 no 2 pp 165ndash177 2003

[13] Z-P Chen Y-L Chen and M Zhong ldquoExperimental studyon axial compression capacity of concrete-filled square steeltubular columns with opening hole damagerdquo BuildingStructure vol 44 no 9 pp 9ndash14 2014 in Chinese

[14] Z-P Chen Y-L Chen andM Zhon ldquoExperimental study onmechanical properties of concrete-filled opening hole dam-aged steel tubular membersrdquo Industrial Construction vol 43no 2 pp 121ndash127 2013

[15] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof octagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 453ndash461 2016

[16] W Xu L-H Han and W Li ldquoPerformance of hexagonalCFST members under axial compression and bendingrdquoJournal of Constructional Steel Research vol 24 no 3pp 309ndash322 2017

[17] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof hexagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 502ndash513 2016

[18] M F Hassanein V I Patel and M Bock ldquoBehaviour anddesign of hexagonal concrete-filled steel tubular short col-umns under axial compressionrdquo Engineering Structuresvol 153 no 12 pp 732ndash748 2017

[19] B Evirgen A Tuncan and K Taskin ldquoStructural behavior ofconcrete filled steel tubular sections (CFTCFSt) under axialcompressionrdquo 6in-Walled Structures vol 80 no 7pp 46ndash56 2014

Advances in Civil Engineering 9

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

[9] A A Nia H Badnava and K F Nejad ldquoAn experimentalinvestigation on crack effect on the mechanical behavior andenergy absorption of thin-walled tubesrdquo Materials amp Designvol 32 no 6 pp 3594ndash3607 2011

[10] X Chang L Fu H-B Zhao and Y-B Zhang ldquoBehaviors ofaxially loaded circular concrete-filled steel tube (CFT) stubcolumns with notch in steel tubesrdquo 6in-Walled Structuresvol 73 no 12 pp 273ndash280 2013

[11] F-X Ding L Fu and Z-W Yu ldquoBehaviors of axially loadedsquare concrete-filled steel tube (CFST) Stub columns withnotch in steel tuberdquo 6in-Walled Structures vol 115 no 6pp 196ndash204 2017

[12] Y Liu and B Young ldquoBuckling of stainless steel square hollowsection compression membersrdquo Journal of ConstructionalSteel Research vol 59 no 2 pp 165ndash177 2003

[13] Z-P Chen Y-L Chen and M Zhong ldquoExperimental studyon axial compression capacity of concrete-filled square steeltubular columns with opening hole damagerdquo BuildingStructure vol 44 no 9 pp 9ndash14 2014 in Chinese

[14] Z-P Chen Y-L Chen andM Zhon ldquoExperimental study onmechanical properties of concrete-filled opening hole dam-aged steel tubular membersrdquo Industrial Construction vol 43no 2 pp 121ndash127 2013

[15] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof octagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 453ndash461 2016

[16] W Xu L-H Han and W Li ldquoPerformance of hexagonalCFST members under axial compression and bendingrdquoJournal of Constructional Steel Research vol 24 no 3pp 309ndash322 2017

[17] F-X Ding Z Li S Cheng and Z-w Yu ldquoComposite actionof hexagonal concrete-filled steel tubular stub columns underaxial loadingrdquo 6in-Walled Structures vol 107 no 11pp 502ndash513 2016

[18] M F Hassanein V I Patel and M Bock ldquoBehaviour anddesign of hexagonal concrete-filled steel tubular short col-umns under axial compressionrdquo Engineering Structuresvol 153 no 12 pp 732ndash748 2017

[19] B Evirgen A Tuncan and K Taskin ldquoStructural behavior ofconcrete filled steel tubular sections (CFTCFSt) under axialcompressionrdquo 6in-Walled Structures vol 80 no 7pp 46ndash56 2014

Advances in Civil Engineering 9

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom